The present invention relates to a pump for pumping high temperature liquids, such as hot oil.
A typical centrifugal pump used for pumping hot liquids usually includes a volute type housing, an adapter, an impeller on a shaft, and a mechanical shaft seal. The mechanical seal must be capable of sealing the hot liquid and containing it within the pump. A disadvantage in such construction of pumps is that seal costs increase greatly when the pump has to be designed to handle liquid temperatures exceeding 400.degree. F.
In the past, to achieve high temperature shaft sealing, expensive and elaborate seals with hard faces or water cooling of the seal cavity with remote heat exchangers have been used. These heat exchangers are expensive to operate because of the large amount of cooling water required. As a result of past experience, there is a need for a pump that is not water cooled, does not use elaborate seals, and which is capable of pumping high temperature liquid.
Prior art pumps, such as those shown in U.S. Pat. No. 4,720,248 and Great Britain Patent Document 728077 disclose attempts made at thermally protecting the motor of the pump but do not contemplate attempting to reduce the temperature of the seal housings or seals. The aforementioned prior art patents show pumps that do not adequately address the problem of insulation of hot liquid from mechanical seals nor of seal wear.
Additionally, some prior air pumps, such those shown in U.S. Pat. No. 4,979,875, utilize long distances from the pump to the seal to allow for adequate dissipation of heat. In some applications it would be preferable for the pump unit to be made as small as possible.